The children weren't discovered until firefighters searched the house.

On Friday, the family gathered around Sims. Her father, James Sims, said she was "broken into a million pieces."

"I think she's in really serious condition," he said.

Authorities wouldn't comment on a possible cause of the fire Friday, but a medical examiner's report notes Jaimey Sims took a shower and hung a damp towel over a lamp to dry before she left the house.

State Fire Marshal's Office spokeswoman Nina Ashley said she couldn't comment on the report.

The towel's placement is one of many things under investigation, said Hillsborough County Fire Rescue Capt. Ray Yeakley.

In general, that wouldn't start a fire, he said. An exception might be if the light bulb were halogen, Yeakley said. "They put off a lot of heat," he said.

Meanwhile, friends mourned with Jaimey Sims and her family.

She worked at the snack bar at the Tampa Yacht and Country Club, where many of the employees knew the twins. James Sims, who worked in maintenance, would sometimes ride the toddlers around on lawn mowers.

Scott Fairbairn, the club's general manager, said all the employees were thinking about Sims and the children's father, Richard Edwards.

"Our thoughts and prayers are with the entire family as they cope with that tragic loss," Fairbairn said.

Times news researcher John Martin and staff writer Jodie Tillman contributed to this report. Jessica Vander Velde can be reached at (813) 226-3433 or jvandervelde@sptimes.com.